A large number of marine organisms have been reported to contain constituents which show antibacterial and antifungal activity in vitro. We have concentrated on those organisms which appear to rely on a chemical defense mechanism for survival. These organisms are often prominent members of the marine fauna and do not appear to have other obvious defense mechanisms to avoid grazing. We have concentrated on sponges, algae and marine bacteria as sources of new antibacterial compounds. We will isolate new compounds having "in vitro" activity against marine bacteria and human pathogens. The compounds will be identified and, in some cases, synthesized. BIBLIOGRAPHIC REFERENCE: Andersen, R.J. and D.J. Faulkner. The synthesis of aeroplysinin-1 and related compounds, J. Amer. Chem. Soc. 97, 936 (1975).